1. Field of the Invention
This invention relates to novel ion exchange/carbon composite materials, methods for their preparation and processes for the removal of heavy metals and other contaminants such as volatile organic compounds (VOC's), chlorine, etc. from aqueous systems utilizing said composite materials.
2. Description of Related Art
Low levels of heavy metals (e.g., lead, cadmium, mercury, etc.) in drinking water are considered detrimental to a person's health and in the case of infants are believed to impede intellectual development. Recognizing these hazards, the Environmental Protection Agency (EPA) has established limits on the presence of heavy metals in drinking water. For example, no more than 15 parts per billion (15 ppb) of lead may be present in public water systems. In addition, industrial water streams must contain less than 0.5 ppm of heavy metals before the water can be discharged. In addition to reducing the heavy metals to acceptable EPA levels, it is desirable to improve the taste, odor and smell of drinking water by removing chlorine, ionic metals, organic molecules and colloidal particles. Ion exchangers, both organic and inorganic, including crystalline molecular sieve zeolites, are known to remove certain metals from aqueous systems such as drinking water. Activated carbon is also used in water purification or remediation processes. Activated carbon improves taste, odor and smell by adsorbing ionic metals, organic molecules and colloidal particles and also removes chlorine.
The purification of drinking water is commonly accomplished at its point of use, e.g., under-the-counter, on-the-counter, whole house systems, under-the-tap, or free standing gravity flow carafe type device. For industrial/commercial applications, packed bed systems are typically used.
There is an ongoing effort to develop improved products which meet or exceed EPA requirements for heavy metals removal as well as improved taste, color and odor, chlorine removal, and have flow rates which are commercially acceptable. Flow rates vary depending the system. For example, flow rates typically vary from 0.05 gallons per minute (gpm) for gravity-flow pour-through carafes to 1.0 gpm or more, e.g., 3.0 gpm-8.0 gpm for devices connected directly to household pressurized water lines.
It is, therefore, the purpose of this invention to provide compositions which provide such improved properties.